High rates of non-vaccinated children throughout the US have reached critical numbers of vulnerable individuals, resulting in perfect conditions for a wildfire storm of measles infections, an easily preventable yet highly contagious disease.

More than 120 confirmed cases of measles have been reported in 17 states and the District of Columbia in the most recent outbreak that started in December 2014 when at least 40 people who visited or worked at the California Disneyland theme park contracted measles.

Over the past two decades, some parents have expressed concern about the safety of routine vaccines in spite of many scientific studies that have demonstrated no evidence of a link between vaccines and later developmental problems.

The Washington National Primate Research Center (WaNPRC) collaborated with the California NPRC to conduct a critical study on the safety of infant vaccines, including measles, in the nonhuman primate (monkey) model. Recently completed, this comprehensive five-year, case-control study closely examined the effects of pediatric vaccines on learning, cognition and social behavior in infants from birth to 12 months of age and found that there was no evidence of adverse development or aberrant behavior in the animals studied, regardless of vaccination status. (Environmental Health Perspectives, February 18, 2015)

One of the most contagious viruses known to science, people with measles can spread the infection for four days before the onset of the rash and four days after. The virus can remain in the air for two hours after an infected person has left the area. However, measles infection is also easily prevented. Before the measles vaccine was given to American children in 1963, there were about 500,000 cases and 450 deaths reported each year. In the past 10 years, there have been an average of 60 cases of measles in the US each year.

Did You Know?

∞ Measles is one of the leading causes of death among young children even though a safe and cost-effective vaccine is available.

∞ In 2013, there were 145,700 measles deaths globally – about 400 deaths every day or 16 deaths every hour.

∞ Measles vaccination resulted in a 75% drop in measles deaths between 2000 and 2013 worldwide.

∞ In 2013, about 84% of the world's children received one dose of measles vaccine by their first birthday through routine health services – up from 73% in 2000.

∞ During 2000-2013, measles vaccination prevented an estimated 15.6 million deaths making measles vaccine one of the best buys in public health.

Children in the US routinely get their first dose of the MMR (measles, mumps, rubella) vaccine at 12 months old or later. The second dose of MMR is generally administered before the child begins kindergarten but may be given one month or more after the first dose. Some children can’t get the vaccine because they have cancer, other diseases that weaken their immune system, or if they are too young (under 6 months of age).

In the 1990s, the mercury-based preservative, thimerosal, was used in most pediatric vaccines. While thimerosal was eliminated from most pediatric vaccines, there are currently two thimerosal-containing vaccines recommended for pediatric use. Parental perceptions that vaccines pose safety concerns are affecting vaccination rates.

The objective of this study conducted at the WaNPRC was to examine the safety of pediatric vaccine schedules in a nonhuman primate model.
 Pregnant rhesus macaque females were provided to Washington from the California NPRC, and vaccines were given to 6 groups of infant male rhesus monkeys born to these females (12–16/group) using a standardized thimerosal dose. Another group received an expanded vaccine schedule, being used in human infants since 2008, that includes multiple doses of rotavirus, hepatitis A, pneumococcal, varicella, and meningococcal vaccines, as well as a yearly influenza vaccine for all children 6 months to 18 years of age. Control animals received saline injections.

Infant development was assessed from birth to 12 months of age by examining the acquisition of standard developmental benchmarks and typical infant social behaviors. Analysis of social and non-social behaviors identified few instances of negative behaviors across the entire infancy period. While some group differences in specific behaviors were reported at 2 months of age, by 12 months all infants, irrespective of vaccination status, had developed the typical repertoire of macaque behaviors.

“This comprehensive five-year, case-control study closely examined the effects of pediatric vaccines on early primate development, and provided evidence of no neurodevelopmental deficits or aberrant behavior in vaccinated animals.”

Measles is deadly for infants and immune-compromised individuals. One out of 1000 people with measles will develop inflammation of the brain, and about one out of 1000 will die. To protect children and adults nationwide, it is recommended that anyone not already immunized against measles get immunized at this time.

The research at WaNPRC was made possible by the CNPRC, which provided the pregnant female rhesus monkeys needed for this study. The California NPRC has a detailed genetic and health information database on each of their animals, resulting in high quality animal models for research.  Selecting the experimental population based upon this information leads to greater uniformity among the animals, which can result in a reduction in animal numbers, since extraneous factors (like vaccine background, health), which might confound the results, are better controlled.

The California NPRC is a national resource conducting research into current human health challenges in all age groups and supporting exceptional nonhuman primate research programs to improve human health. It has comprehensive capabilities, resources and support for research collaborations, services, and training including study design and new model development.

Additionally, the California NPRC is working to expand its research portfolio through implementation of a research stimulus program. This new program is enhancing collaboration and outreach to the biomedical and pharmaceutical industries, research institutions, and private foundations. Projects supported under this cost-saving program allow for increased size and scope of studies using nonhuman primates, leading to novel discoveries and projects. Contact us at www.CNPRC.UCDavis.edu for more information.

Examination of the Safety of Pediatric Vaccine Schedules in a Non-Human Primate Model: Assessments of Neurodevelopment, Learning, and Social Behavior. Feb 18, 2015. Britni Curtis, Noelle Liberato, Megan Rulian, Kelly Morrisroe, Caroline Kenney, Vernon Yutuc, Clayton Ferrier, C. Nathan Marti, Dorothy Mandell, Thomas M. Burbacher, Gene P. Sackett and Laura Hewitson. Environ Health Perspect; DOI:10.1289/ehp.1408257